Ecosystem, Food Chain, Ecological Pyramid

Ecosystem: the unity of a community of living organisms (biocenosis) and the environment they live in (biotope).

Components

• Producers: autotrophs, green plants. The chain begins with them.
• Consumers: animals.
• Decomposers: decomposing bacteria and fungi.

Food chain:

1. Plant (producer)
2. Herbivore (1st-order consumer)
3. Predator (2nd-order consumer)

Ecological pyramid

Lindeman's rule: to each next trophic level about 10% of the energy of the previous level is transferred. 90% is spent on life processes and dissipated as heat.

There are three types of pyramids: pyramid of numbers, pyramid of biomass, and pyramid of energy.

Level	Energy
Producer (plant)	100%
1st-order consumer	10%
2nd-order consumer	1%
3rd-order consumer	0,1%

From the producer to the 2nd order, 1% is transferred, not 10%.

Key facts

• The 1st-order consumer is a herbivore. The 2nd-order consumer is a predatory or insectivorous animal.
• Matter circulates in the ecosystem, energy flows in one direction (beginning from the Sun).
• The energy pyramid always decreases from bottom to top. The pyramid of numbers can sometimes be inverted (tree and insect).
• Agrocenosis: an artificial ecosystem created by humans, has low stability, requires additional energy (fertilizer, irrigation).
• A food chain usually does not exceed 4-5 links.